On Jan. 22, the night before Lauren Smith-Fields would have turned 24, her friends gathered to celebrate the birthday of another friend. They talked, listened to music. And then “Good Days” by SZA began to play.

Ray Rose, 22, started to cry. He looked around the room and noticed that some of his friends were crying too. Mr. Rose thought about how Ms. Smith-Fields never knew the words to any songs, but she knew the words to this one. It was her favorite.

He stepped outside and pulled up a video he had made two weeks earlier, featuring clips of the two of them during their high school years. He made it as a way to remember Ms. Smith-Fields, who had been found dead in her apartment in Bridgeport, Conn., on Dec. 12 after a Bumble date. He decided to post the video to TikTok, and then turned off his phone.

The video now has more than 1.4 million views, more than 440,000 likes and thousands of comments. In it, Mr. Rose and Ms. Smith-Fields are walking outside on a sunny day with brimming smiles, singing on a stage and dancing in unison. “Good Days” plays in the background. “i literally just a shed a tear i can’t believe this still. i love you,” Mr. Rose wrote in the caption.

Ms. Smith-Fields was a student at Norwalk Community College who wanted to become a physical therapist. Her family and friends described her personality as vibrant and magnetic.

Her mother, Shantell Fields, has said that she didn’t find out about her daughter’s death for nearly two days — and that she learned the news not from the Bridgeport Police Department, but through a landlord. Her lawyer said the family had to beg the department to collect evidence found in the apartment.

As weeks passed with few updates provided to the family and little media attention on the case, TikTok videos about Ms. Smith-Fields, many featuring footage of her family’s emotional pleas for help, began to garner more and more attention. Her friends began to post clips too, showing how playful and energetic she was. And in lieu of news from the Police Department, amateur sleuths began making videos in which they tried to answer big questions about the case themselves.

The videos about Ms. Smith-Fields have since garnered millions of views and hundreds of thousands of comments. The hashtags #laurensmithfields and #justiceforlaurensmithfields have been viewed more than 27 million times each on TikTok.

A spokesman for the Bridgeport Police Department declined to comment on the posts, citing the open status of the case.

But it was not until late January, after the outpouring of questions on social media and a march by Ms. Smith-Fields’s family members and supporters, that the mayor made his first public statement about the case. The Connecticut Office of the Chief Medical Examiner then released Ms. Smith-Fields’s cause of death: an accidental overdose of fentanyl combined with prescription medication and alcohol.

Once those findings were released, the Police Department opened a criminal investigation and the detective who handled Ms. Smith-Fields’s case was suspended.

Advocacy groups for Black women are certain that the TikTok videos made a difference.

“Social media is utterly important,” said Dawn Rowe, the president of Girl Vow, a New York-based nonprofit that recently started a task force to find missing and murdered women of color.

Word slowly began to spread about Brenda Lee Rawls, too. Ms. Rawls, like Ms. Smith-Fields, was a Black woman who was found dead in Bridgeport on Dec. 12.

Ms. Rawls’s relatives said they learned about her death, at the age of 53, not through the Police Department, but through a neighbor. Her cause of death is still unknown, and the detective who oversaw her case has been suspended as well.

Natalie Wilson, the co-founder of the Black and Missing Foundation, a national nonprofit that works to bring attention to the cases of missing people of color, said social media had been instrumental in focusing attention on the stories of Black women who have died.

She cited the cases of Sandra Bland, who was found hanged in a jail cell after a traffic stop in 2015, and Breonna Taylor, a Black medical worker who was killed by the police in Louisville, Ky., five years later.

“We can’t wait on the news cycle, we can’t wait for someone to greenlight a story,” said Ms. Wilson. “We’re utilizing social media and it has been effective,” she said.

Ms. Rowe described it as the only platform “that people of color have to discuss their pain and failures of a broken system.”

Jared Stokes, 31, appears to have posted the first TikTok video about Ms. Smith-Fields. His video, posted on Dec. 27, highlighted coverage from News 12 Connecticut, the first news outlet to cover the story, noting that the man Ms. Smith-Fields had been on a date with, who was white, hadn’t been brought in for questioning.

He also noted the intense focus the case of Gabrielle Petito, a 22-year-old white woman who went missing last September and was later found strangled to death, had received, and the comparatively little attention paid to Ms. Smith-Fields’s case.

“I just know that a lot of times stories about Black women, Black kids don’t really get much traction,” said Mr. Stokes, who lives in Maryland and is the founder of a media education company focused on Black affairs. “I just put it out and said, ‘OK, hopefully, this gets traction, and hopefully her family gets justice for this.’”

The post took off, and other users later credited it in their own videos. But it wasn’t until Ms. Smith-Fields’s friends had posted that onlookers were able to see intimate looks at her life.

“We have to start posting more because they need to see how Lauren was a person,” Mr. Rose said he told his friend group.

Another friend, Miryam Abdul-Hakeem, 23, spent hours sifting through the clips she had featuring Ms. Smith-Fields on her phone. One of the videos she posted has received 2.1 million views on TikTok, and more than 450,000 comments.

“A lot of these fill my heart,” Ms. Abdul-Hakeem said of the comments her videos have received. “Some of them make me sad because some people tag their best friend. It’s a comment that says like, ‘I don’t know what I’d do without you.’ That makes me really sad.”

People from all over the world, including the United Kingdom, the Netherlands, and Italy, have commented on the TikTok posts of another close friend, Verónica DeLeon, 22. She said that her friend had a community of people who cared deeply about her and would fight for her.

“I don’t know what anyone thought, but Lauren was the right one,” said Ms. DeLeon. “You got the right girl, we’re going to come hard behind her.”

When Justin Evans-Smith, Ms. Smith-Fields’ cousin, first saw strangers posting about her on social media, he said, it made his stomach hurt. But it also made him feel like something monumental was happening.

“This is bigger than us, this is going to be a movement,” said Mr. Evans-Smith, 24.

He said he saw a clear link between his cousin’s case and the broader Black Lives Matter movement.

“The way that Lauren’s case was treated, it just follows into the fact that Black lives aren’t treated as well as everybody else,” he said, adding that he thinks her case would have been handled differently by the Police Department if Ms. Smith-Fields had been a white woman and the last person she was with had been a Black man.

He thinks her case would have been handled differently by the news media, too.

While News 12 Connecticut and several Black-run outlets covered both Ms. Smith-Fields and Ms. Rawls in December, it wasn’t until late January that most national publications began to publish articles about the cases. And the volume of coverage has paled in comparison to the number of articles written about Ms. Petito.

Ms. Wilson of the Black and Missing Foundation believes the imbalance reflects a bias in newsrooms, many of which are still predominantly white.

“The gatekeepers don’t look like us, so they aren’t telling the stories of Black and brown people,” she said. “We need to have more diversity, more diversity in newsrooms so that our stories can be told.”

Until then, many families must do the best they can to get the word out about their lost ones.

“There’s a loss of hope in families a lot of times, so we’re talking about families who don’t have the wherewithal to push their own narratives, push their own stories, because the fight is so heavy,” said Ms. Rowe of Girl Vow. “The burdens are so heavy, the grief is heavy.”

Dorothy Washington, one of Ms. Rawls’s sisters, said she planned to enlist the help of younger family members to raise awareness online, including her 17-year-old grandson who aspires to be a computer engineer.

“My sister is in her 50s, I’m in my 50s,” Ms. Washington said. “We don’t use social media that much.”